The Golden Gate Bridge is a suspension bridge spanning the Golden Gate strait, the one-mile-wide (1.6 km), three-mile-long (4.8 km) channel between San Francisco Bay and the Pacific Ocean. The structure links the American city of San Francisco, California – the northern tip of the San Francisco Peninsula – to Marin County, carrying both U.S. Route 101 and California State Route 1 across the strait. The bridge is one of the most internationally recognized symbols of San Francisco, California, and the United States. It has been declared one of the Wonders of the Modern World by the American Society of Civil Engineers. The Frommers travel guide describes the Golden Gate Bridge as "possibly the most beautiful, certainly the most photographed, bridge in the world." It opened in 1937 and was, until 1964, the longest suspension bridge main span in the world, at 4,200 feet (1,300 m). Before the bridge was built, the only practical short route between San Francisco and what is now Marin County was by boat across a section of San Francisco Bay. A ferry service began as early as 1820, with a regularly scheduled service beginning in the 1840s for the purpose of transporting water to San Francisco.